Field
Packaging for microelectronic devices.
Description of Related Art
Microelectronic packaging technology, including methods to mechanically and electrically attach a silicon die (e.g., a microprocessor) to a substrate or other carrier continues to be refined and improved. Bumpless Build-Up Layer (BBUL) technology is one approach to a packaging architecture. Among its advantages, BBUL eliminates the need for assembly, eliminates prior solder ball interconnections (e.g., flip-chip interconnections), reduces stress on low-k interlayer dielectric of dies due to die-to-substrate coefficient of thermal expansion (CTE mismatch), and reduces package inductance through elimination of core and flip-chip interconnect for improved input/output (I/O) and power delivery performance.
One issue that arises with a package, such as a BBUL, is warpage. A BBUL package typically consists of a dielectric material, possibly of a number of films, separating conductive lines or traces of a material such as copper. The package is also typically considerably larger than the die. Accordingly, when combined with a rigid die, the combination including a significantly larger package can experience warpage. Any such warpage may be acceptable in those instances where the combination of die and package constitute a complete structure. However, one trend is to connect at least one additional package to the BBUL/die package such as package on package (POP) configurations or stacked on a die (e.g., a through silicon via (TSV) die, e.g., wide I/O packaging. In such case, alignment and stability of connections becomes more significant.